The objective of this study was to find out the differences and relation of morphologically abnormal spermatozoa incidence (MASI) to seminal plasma (SP), testosterone, oestradiol, concentration of ions and alleles of prolactin receptor (PRLR) gene. Therewere no significant differences among boars in semen volume and sperm concentration. The results of this study lead to the conclusion the differences between boar SP components and frequency of PRLR alleles correlate with MASI variability.